1. Field of the Invention
Vulcanized rubber is conventionally reclaimed by subjecting it to heat and pressure, often in the presence of suitable oils and/or chemicals, and certain screw machines have been found to be desirable for these purposes. After being reclaimed, refining processes are used to smooth the product.
2. Description of the Prior Art
In U.S. Pat. Nos. 2,653,348, 2,653,349 and 2,653,915, issued Sept. 29, 1953 to Elgin and Sverdrup, and 3,051,990 issued Sept. 4, 1962 to Peterson, there are described processes and apparatus for reclaiming previously-vulcanized rubber wherein the rubber (e.g. ground tire stock) is fed to a screw rotating inside a stationary cylindrical chamber and adapted to effect a shearing action on the rubber and to generate heat therein and is then expelled or discharged through an annular channel.
In the conventional subsequent refining steps the product (previously-vulcanized rubber in reclaimed form) is squeezed between rolls and wound up into many layers to form a sheet on a wind-up drum, and cut when the wind-up drum is full. The purpose of the squeezing between rolls is to break down the particles of reclaimed rubber and to smooth them out to form a homogeneous sheet; but the current process requires a great deal of attention and labor.
Various types of apparatus having stator and rotor surfaces without screw flights or like propulsion means on the rotor have been proposed for extruding elastic melt material and similar substances. Examples of these are the Maxwell U.S. Pat. Nos. 3,046,603, 3,554,041 and 3,790,328; but, in spite of their effectiveness in the melt-extrusion field, they have neither been suggested for or adapted to the reclaiming of rubber or the refining of reclaimed rubber, nor have processes therefor been disclosed or suggested.